There have been developed various LED lamps using a semiconductor light-emitting element such as an LED (Light-emitting Diode), and having high efficiency and a long life, instead of a general lighting fixture such as a halogen bulb. There are problems that when an LED becomes a high temperature because of heat generated by the LED, light-emitting efficiency decreases and thus light output of a lamp decreases and life of the LED becomes short. Therefore, there has been known that the LED lamp of this type includes a heat sink that dissipates heat emitted from the LED (see Patent documents 1 to 4).